1. Field of the Invention
This invention relates generally to improvements in a vent control valve attached to a fuel filler tube of a fuel tank, for example, of an automotive vehicle, and more particularly to such a vent control valve which does not require a larger space therefor.
2. Description of the Prior Art
A fuel filler tube of a fuel tank is usually provided with a vent tube for communicating the inside of the fuel tank with the filler tube near the open end in order to vent fuel vapor in the fuel tank during fuel filling. However, the fuel vapor is unavoidably emitted through the open end of the filler tube to ambient air thereby contaminating air.
In view of this problem, a variety of devices have hitherto proposed and put into practical use. One of them is an arrangement in which fuel vapor in the fuel tank is introduced through an evaporation tube to a vapor storage canister, in which the fuel vapor is purged with purge air to be supplied to an intake system of an engine. Another is an arrangement in which the open end of the filler tube is sealed upon inserting a fuel supply gun or nozzle thereinto to prevent fuel vapor from emission to the outside of the fuel tank during fuel filling without any trouble. A concrete example of such devices will be discussed with reference to FIG. 5 as disclosed in Japanese Utility Model Provisional Publication No. 61-67238. In the device of FIG. 5, a door 3 is disposed inside a fuel filler tube 1 at a portion near the open end 1a and constructed to pivotally move around a hinge pin 3a to open when the fuel supply gun 2 is inserted into the filler tube 1.
A vent control valve 4 is attached to the filler tube 1 in such a manner that a rod 5 thereof is projectable through the opening 1b into the filler tube 1. The tip end 5a of the rod 5 can be pushed upwardly by the door 3 so as to control passage of fuel vapor from a fuel tank to a vapor storage canister. More specifically, the vent control valve 4 is provided at its inside with a partition wall 10 which defines first and second chambers 8, 9 on the opposite side thereof. The first chamber 8 is supplied with fuel vapor through a check valve 7 from a vent tube 6 connected to the fuel tank. The partition wall 10 is formed with a central opening 10a which is closable with a valve member 11 fixed to the rod 5 at the intermediate section. A diaphragm 12 is provided to insulate the second chamber 9 from the opening 1b and the inside of the filler tube 1 in order to prevent liquid fuel from flowing in from the filler tube 1 to the second chamber 9. A spring 14 is disposed between the partition wall 10 and the spring seat 13 fixedly attached to the diaphragm 12. A tube 15 is connected to the vent control valve 4 to communicate the second chamber 9 with the vapor storage canister.
With this vent control valve 4, when the fuel supply gun 2 is inserted into the filler tube 1 at the portion near the open end 1a, the door 3 is pivotally moved in the direction of an arrow A thereby to push up the tip end 5a of the rod 5. Then, the rod 5 moves upwardly against the bias of the spring 14 moving the valve member 11 in the direction of an arrow B, i.e., from the state indicated by solid lines to the state indicated in phantom. As a result, the first and second chambers 8, 9 are brought into communication with each other. Accordingly, fuel vapor flowing out of the fuel tank T through the vent tube 6 flows through the first and second chambers 8, 9 and introduced into the vapor storage canister as indicated by an arrow C. The fuel vapor is once absorbed in activated charcoal in the canister and then purged with purge air during engine operation to be supplied to the intake system of the engine.
However, difficulties have been encountered in the above-discussed vent control valve 4, in which the vent control valve 4 unavoidably projects radially outwardly as a whole from the fuel filler tube 1 since the first and second chambers 8, 9 are located one upon another generally in the radially outward direction relative to the filler tube 1. Accordingly, in installation of the filler tube 1 to the vehicle, a space for the vent control valve 4 is necessary on the vehicle body side thereby decreasing the freedom in design of the vehicle. Additionally, the thus outwardly projecting vent control valve tends to be damaged by careless or sudden impact from the outside.